[Term Entry] C++ Strings: .append()

* Created term entry for .append() method for C++ strings

* minor fixes

* Update append.md

* Update append.md

* Update append.md

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Author: BrianNazir

content/cpp/concepts/strings/terms/append/append.md

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+---
+Title: '.append()'
+Description: 'Appends characters or strings to the end of an existing string.'
+Subjects:
+  - 'Code Foundations'
+  - 'Computer Science'
+Tags:
+  - 'Characters'
+  - 'Concatenation'
+  - 'Methods'
+  - 'Strings'
+CatalogContent:
+  - 'learn-c-plus-plus'
+  - 'paths/computer-science'
+---
+
+In C++, **`.append()`** is a method that concatenates new characters to the end of an existing string without requiring reassignment. It can be used to combine two different strings, append a portion of a string (also known as a substring), or add specific characters to the end of a string.
+
+## Syntax
+
+```pseudo
+str.append(str2);               // Appends entire string
+str.append(str2, pos, len);     // Appends substring from str2
+str.append(n, char);            // Appends character 'char' n times
+str.append(first, last);        // Appends range using iterators
+```
+
+**Parameters:**
+
+- `str2`: The string to append or extract a substring from.
+- `pos`: The starting index in `str2` (used when appending a substring).
+- `len`: The number of characters to append from `str2`, starting at `pos`.
+- `n`: The number of times to append the character `char`.
+- `char`: A character to be appended multiple times.
+- `first`, `last`: Iterators defining a range of characters to append.
+
+**Return value:**
+
+Returns a reference to the modified string (`*this`), allowing method chaining.
+
+## Example 1: Appending Two Strings Together
+
+This example takes two separate strings and concatenates them:
+
+```cpp
+#include <iostream>
+#include <string>
+using namespace std;
+
+int main () {
+  string stringOne = "Hello ";
+  string stringTwo = "World!";
+
+  //Appends stringTwo to the end of stringOne
+  stringOne.append(stringTwo);
+
+  cout << stringOne;
+  return 0;
+}
+```
+
+The output produced by this code is:
+
+```shell
+Hello World!
+```
+
+## Example 2: Appending One Piece of a String to Another
+
+This example takes a portion of one string and adds it to the end of another string:
+
+```cpp
+#include <iostream>
+#include <string>
+using namespace std;
+
+int main() {
+  string str1("Straw Hat ");
+  string str2("Monkey D. Luffy");
+
+  // Appends 5 characters from index 10 of str2 to str1
+  str1.append(str2, 10, 5);
+
+  cout << str1;
+  return 0;
+}
+```
+
+The output produced by this code is:
+
+```shell
+Straw Hat Luffy
+```
+
+## Codebyte Example: Appending Multiple Characters to a String
+
+This codebyte example takes a specific character and adds it a specific amount of times to the end of a string:
+
+```codebyte/cpp
+#include <iostream>
+#include <string>
+using namespace std;
+
+int main() {
+  string str("Codecademy is awesome");
+
+  // Appends 3 occurrences of '!' to the end of str
+  str.append(3, '!');
+
+  cout << str;
+
+  return 0;
+}
+```